Manuel C Casaje Jr

Electrical Line Faults Manuel C Casaje Jr

The derivation of formulas in solving electrical line faults is made simpler by just following the directions of the flow of currents and the voltage paths indicated in the modified circuit diagrams. Another method is by using graphically the Phasor A and J Diagram which include both the values of complex numbers in rectangular and polar forms. The equivalent single phase and sequence network diagrams are drawn indicating the three lines and the neutral line instead of a single line only. Shown alongside fault currents are the fault voltages for easier analysis and comparison between the two results. Also explained are how the symmetrical sequence network and phasor (vector) diagrams are used to determine the possible consequences of the three basic types of electrical line faults such as Short-Circuit Faults, Open-Circuit Faults, and the Simultaneous Faults. Different types of faults create different magnitudes of fault currents. Any part of the equipment must be quickly disconnected or removed from the power source in case of short-circuits. The ratings and settings of protection devices must also deal with the consequences of fault currents. Setting a circuit breaker beyond its rated interrupting time, that is to open a faulted circuit breaker at high speed (within the first half or up to one cycle on a high current fault), will create a significant hazard. Circuit breakers have to be adjusted to trip at a lower speed for them to interrupt the flow of fault current within their interrupting capacity. For higher speed requirement, the ampere rating of the circuit breaker has to be bigger than the available fault current on a circuit.